1. Field of the Invention
The present invention relates generally to soil-cement compositions and methods, and more particularly, to improved soil-cement compositions and methods of utilizing them in jet grouting operations and the like.
2. Description of the Prior Art
A variety of procedures have been developed for forming cementitious subterranean containment walls, foundations, pilings and the like comprised of soil-cement compositions. In such procedures, an aqueous cement slurry containing soil is placed in a subterranean location and allowed to set into a hard cementitious mass having compressive strength therein. The soil-cement compositions which have been utilized have generally been comprised of a hydraulic cement, water, a dispersant and soil. The presence of the soil in the compositions reduces the cost of the compositions as well as the quantities of removed soil to be disposed of.
A relatively simple prior art procedure for forming and placing a soil-cement composition in the ground involves excavating a hole in the ground, mixing a portion of the excavated soil with water and hydraulic cement on the surface, placing the soil-cement composition formed in the hole and allowing it to set into a hard cementitious mass therein. More recently, procedures for simultaneously forming a subterranean cavity and mixing and placing a soil-cement composition therein generally known as "jet grouting" have been developed and used. The jet grouting procedure basically comprises the steps of drilling and/or enlarging a hole in the ground and forming a soil-cement composition therein by means of high velocity jets of an aqueous cement slurry. That is, the aqueous cement slurry is pumped through a string of pipe and through jet forming ports, usually at the bottom of the pipe and/or in a drill connected thereto, at a pressure and rate sufficient to produce high velocity jets of cement slurry which cause soil to be mixed with the cement slurry. A substantial quantity of excess soil-cement slurry is formed in the process which is moved upwardly through the open hole to the surface which often must be removed and disposed of.
Another similar procedure sometimes referred to as the "auger-jet foundation procedure" utilizes a drill connected to a string of pipe which drills a hole in the ground of the approximate size required, and an aqueous cement slurry is mixed with the soil produced at the bottom of the hole by pumping the cement slurry down the string of pipe and through openings therein or in the drill. The auger-jet procedure is different from jet grouting in that high velocity jets of the cement slurry are not utilized to enlarge the hole. The rate of drilling by the drill, i.e., the rate that soil is produced, is controlled in proportion to the rate of cement slurry mixed with the soil to thereby produce a soil-cement composition having desired properties. Again, however, the excess soil-cement composition formed flows out of the hole and generally must be removed and disposed of.
The disposal of the excess soil-cement composition formed has heretofore been and continues to be a problem in both the jet grouting and auger-jet procedures. The soil-cement composition which exits the hole and accumulates on the surface generally has a high viscosity whereby it has only limited pumpability, if any, and moving it to a disposal location has been time consuming and expensive. While various cement and soil dispersants have been utilized in the soil-cement compositions formed in attempts to lower the viscosities of the compositions, such dispersants have not been adequate to alleviate the handling and disposal problems encountered. Thus, there is a need for improved soil-cement compositions and methods of forming such compositions whereby the compositions can be mixed, pumped, processed and disposed of in an easier, cost effective manner.